Benefits of Hyperbaric Medicine

Benefits of Hyperbaric Oxygen Therapy (HBOT)

There are a number of beneficial physiological effects associated with intermittent exposure to high-dose oxygen. These mechanisms of action are employed in the management of a variety of disease states.

Hyperoxygenation – For pressures above 2.5 ATA, sufficient quantities of oxygen can be dissolved in the plasma alone to support life in the absence of red blood cells. The clinical implications of this mechanism for the salvage or support of injured tissue with marginal perfusion are clear.

Vasoconstriction – As a drug, oxygen is unique because it is the only agent capable of inducing mild vasoconstriction while simultaneously elevating tissue pO2 levels. Hyperoxia-induced reductions in blood flow are more than offset by the large increase in delivered oxygen. The clinical implications are important when dealing with injured tissue where interstitial edema introduces a diffusion barrier and, in some cases, impedes microcirculatory flow. HBO has the capacity to support injured edematous tissue while simultaneously reducing excess interstitial fluid. In more acute situations, HBO may prevent the evolution of edema altogether.

Neovascularization – For most patients, local hypoxia is a significant part of the problem of non-healing or "problem" wounds. The use of transcutaneous oximetry allows for a more accurate identification of those wounds in which the cells are too hypoxic to respond to the reparative call of local growth factors. Because HBO provides intermittent elevations in oxygen, it is capable of literally breathing new life into hypoxic tissue. Under the influence of HBO, new blood vessels bud into these pathologically hypoxic wounds.

Antibacterial effects – Despite the very high arterial pO2 achieved with HBO, the tissue levels in the heart of necrotic wounds may only achieve 100 to 200 mm Hg. Although such levels are not bacteriocidal to anaerobes, they are bacteriostatic. As such, oxygen behaves like many bacteriostatic antibiotics by containing the infection and allowing normal host defense mechanisms to eradicate infection. In addition, HBO has been shown to produce a direct synergistic effect with numerous antibiotics. HBO also exerts an indirect synergism by converting anaerobic wounds with a low pH to aerobic wounds characterized by normal pH. This pH shift is important, as many antibiotics do not work well at an acid pH.

Leukocyte oxidative killing – Although phagocytosis is relatively unhindered by an anaerobic environment, the killing capacity of neutrophils is markedly reduced. Phagocytosis per se does not kill bacteria; the actual destruction of bacteria is a complex interaction of neutrophil enzymes with neutrorphil-generated oxygen radicals. By providing supplemental oxygen, HBO "turbo charges" the destructive capacity of the neutrophil.

Attenuation of reperfusion injury – Following an ischemic interval, the total injury pattern is the result of two components: a direct and irreversible injury from hypoxia and an indirect injury, which is largely mediated by the inappropriate activation of leukocytes. Hyperbaric oxygen reduces the indirect component of injury by preventing the inappropriate activation of leukocytes. The net effect is the preservation of marginal tissue that would otherwise be lost to ischemia-reperfusion injury. The potential clinical implications are enormous for any clinical scenario in which there has been a significant interruption of blood flow.